This invention relates to a data recording/reproducing method and a data send-out method. More particularly, it relates to a data recording/reproducing method in a so-called near video-on-demand for time-differentially distributing e.g. cinema films.
In the near video-on-demand in which continuous data is simultaneously outputted over plural channels, for example, compressed data obtained on encoding picture signals of a cinema in accordance with a pre-set encoding system is distributed time-differentially, data for a cinema are written in a so-called mass storage whose access time is significantly higher than the data transfer rate, such as a magnetic disc device, referred to hereinafter as a hard disc device, or a magneto-optical disc, and are read out from plural optional places of the recording medium, so that continuous multi-channel data having different distribution time points can be outputted simultaneously, that is in parallel.
Meanwhile, if cinema data is sequentially recorded, beginning from the leading frame of the cinema, in a direction from the outer rim towards the inner rim of the magnetic disc provided in the hard disc device, the magnetic disc has to seek a long distance since reading the last frame until reading the leading frame, thus significantly protracting the access time. Consequently, for outputting data continuously, that is without interruption, it is necessary to employ a large capacity buffer memory in order to take the maximum access time into account.
In other words, if, when reading out data from a mass storage in the near video-on-demand for outputting continuous data over plural channels in parallel, the number of channels is to be increased, it is necessary to provide a mass storage of a higher speed and a buffer memory of a larger capacity in order to take the maximum access time into account.